package com.gitee.cliveyuan.tools.img;

import com.gitee.cliveyuan.tools.Assert;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

/**
 * @author clive
 * Created on 2018/07/27
 * @since 1.0
 */
public class ImgTypeTools {

    private static final String TYPE_JPG = "jpg";
    private static final String TYPE_GIF = "gif";
    private static final String TYPE_PNG = "png";
    private static final String TYPE_BMP = "bmp";
    private static final String TYPE_UNKNOWN = "unknown";


    /**
     * 获取图片真实格式
     *
     * @param imgPath 图片路径
     */
    static String getImgType(String imgPath) {
        try {
            Assert.notEmpty(imgPath, "img file is required");
            File file = new File(imgPath);
            Assert.isTrue(file.exists(), "img file not exists");
            return getImgType(new FileInputStream(file));
        } catch (FileNotFoundException e) {
            throw new IllegalArgumentException("img file not found");
        }
    }

    /**
     * 根据文件流判断图片类型
     *
     * @param fis
     * @return jpg/png/gif/bmp
     */
    private static String getImgType(FileInputStream fis) {
        //读取文件的前几个字节来判断图片格式
        byte[] b = new byte[4];
        try {
            fis.read(b, 0, b.length);
            String type = bytesToHexString(b).toUpperCase();
            if (type.contains("FFD8FF")) {
                return TYPE_JPG;
            } else if (type.contains("89504E47")) {
                return TYPE_PNG;
            } else if (type.contains("47494638")) {
                return TYPE_GIF;
            } else if (type.contains("424D")) {
                return TYPE_BMP;
            } else {
                return TYPE_UNKNOWN;
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fis != null) {
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return null;
    }

    /**
     * byte数组转换成16进制字符串
     *
     * @param src
     */
    private static String bytesToHexString(byte[] src) {
        StringBuilder stringBuilder = new StringBuilder();
        if (src == null || src.length <= 0) {
            return null;
        }
        for (int i = 0; i < src.length; i++) {
            int v = src[i] & 0xFF;
            String hv = Integer.toHexString(v);
            if (hv.length() < 2) {
                stringBuilder.append(0);
            }
            stringBuilder.append(hv);
        }
        return stringBuilder.toString();
    }

}
